Haven't posted here in a while, but I think I've come up with a very efficient way of finding if a number is prime, using TI-BASIC for use with TI-83/84/+/SE calculators. I am trying to optimize it however possible :)

:Input "NUMBER: ",A
:If A<2 or fPart(A
:Then
:Disp "INVALID INPUT"
:Stop
:End
:0→B
:2→I
:While I<A and not(B
:If 0=fPart(A/I
:1→B
:I+2→I
:If I=4
:3→I
:End
:If B
:Disp "NOT"
:Disp "PRIME"

A few notes:

• Lines 2-6 are for validating input, and don't affect the effectiveness of the program.
• The closing "s on line 4 and the last two lines are not necessary, but I added them so the syntax would highlight nicely here.
• Lines 12-14 are for speeding up the loop doubly; instead of incrementing by 1 each time, it is by 2, with the If to offset the 4 to 3 on the first run.
• The not(B was very efficient, to end the loop whenever a match to identify the number as a composite number is found.

I've come up with a very efficient way of finding if a number is prime, using TI-BASIC for use with TI-83/84/+/SE calculators. I am trying to optimize it however possible.

:Input "NUMBER: ",A
:If A<2 or fPart(A
:Then
:Disp "INVALID INPUT"
:Stop
:End
:0→B
:2→I
:While I<A and not(B
:If 0=fPart(A/I
:1→B
:I+2→I
:If I=4
:3→I
:End
:If B
:Disp "NOT"
:Disp "PRIME"

A few notes:

• Lines 2-6 are for validating input, and don't affect the effectiveness of the program.
• The closing "s on line 4 and the last two lines are not necessary, but I added them so the syntax would highlight nicely here.
• Lines 12-14 are for speeding up the loop doubly; instead of incrementing by 1 each time, it is by 2, with the If to offset the 4 to 3 on the first run.
• The not(B was very efficient, to end the loop whenever a match to identify the number as a composite number is found.

Haven't posted here in a while, but I think I've come up with a very efficient way of finding if a number is prime, using TI-BASIC for use with TI-83/84/+/SE calculators. I am trying to optimize it however possible :)

:Input "NUMBER: ",A
:If A<2 or fPart(A
:Then
:Disp "INVALID INPUT"
:Stop
:End
:0->B
:2->I
:While I<A and not(B
:If 0=fPart(A/I
:1->B
:I+2->I
:If I=4
:3->I
:End
:If B
:Disp "NOT"
:Disp "PRIME"

A few notes:

• I represented the STO arrow with ->.
• Lines 2-6 are for validating input, and don't affect the effectiveness of the program.
• The closing "s on line 4 and the last two lines are not necessary, but I added them so the syntax would highlight nicely here.
• Lines 12-14 are for speeding up the loop doubly; instead of incrementing by 1 each time, it is by 2, with the If to offset the 4 to 3 on the first run.
• The not(B was very efficient, to end the loop whenever a match to identify the number as a composite number is found.

Haven't posted here in a while, but I think I've come up with a very efficient way of finding if a number is prime, using TI-BASIC for use with TI-83/84/+/SE calculators. I am trying to optimize it however possible :)

:Input "NUMBER: ",A
:If A<2 or fPart(A
:Then
:Disp "INVALID INPUT"
:Stop
:End
:0→B
:2→I
:While I<A and not(B
:If 0=fPart(A/I
:1→B
:I+2→I
:If I=4
:3→I
:End
:If B
:Disp "NOT"
:Disp "PRIME"

A few notes:

• Lines 2-6 are for validating input, and don't affect the effectiveness of the program.
• The closing "s on line 4 and the last two lines are not necessary, but I added them so the syntax would highlight nicely here.
• Lines 12-14 are for speeding up the loop doubly; instead of incrementing by 1 each time, it is by 2, with the If to offset the 4 to 3 on the first run.
• The not(B was very efficient, to end the loop whenever a match to identify the number as a composite number is found.